Cannot install Support SSH Access Extension on Debian 9, Ubuntu 18.04: Another installation is currently in progress

Symptoms

• Plesk is installed on Debian 9 or Ubuntu 18.04:

  # plesk -v | grep 'OS version'
  OS version: Debian 9.12 x86_64

• Support SSH Access Extension requires installation of sudo command but it fails with the following error in Extensions > Support SSH Access Extension:

  Another installation is currently in progress

  OR

  In order to proceed, package "sudo" must be installed on the server.

• There are no Plesk Installer, dpkg or apt processes running on the server:

  # ps auxfww | less | grep installer
  root 23279 0.0 0.0 12716 952 pts/0 S+ 11:32 0:00 _ grep installer

  # ps auxfww | less | grep dpkg
  root 23279 0.0 0.0 12716 952 pts/0 S+ 11:32 0:00 _ grep dpkg

  # ps auxfww | less | grep apt
  root 23279 0.0 0.0 12716 952 pts/0 S+ 11:32 0:00 _ grep apt

Cause

Bug with ID EXTCERT-2781 in Support SSH Access Extension installation.

Resolution

1. Login server via SSH;

2. Run the following command to install sudo manually:

   # apt install sudo -y && rm /usr/local/psa/var/modules/support-access/*